Heat treating apparatus for web and sheet material



Oct. 1, 1968 H- L. SMITH, JR

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ATTORNEYS Oct. 1, 1968 H. 1.. SMITH, JR

HEAT TREATING APPARATUS FOR WEB AND SHEET'MATERIAL 7 Sheets-Sheet 5Original Filed March 24, 1966 $1 53 .53 22 213mm 5&3 -m 3 8 58 212mm 585&8 2

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HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL 7 Sheets-Sheet 4Original Filed March 24, 1966 ATTORNEYS mzw Oct. 1, 1968 H. 1.. SMITH,JR 3,403,454

HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL 7 Sheets-Sheet 5Original Filed March 24, 1966 INVENTOR Horace L. Smith, Jr.

ATTORNEYS '7 Sheets-Sheet 6 H. L. SMITH, JR

HEAT TREATING APPARATUS FOR WEB AND SHEET MATERIAL K W ATTORNEYS Oct. 1,1968 3,403,454

HEAT TREATING APPARATUS FOR was AND SHEET MATERIAL H. 1.. SMITH, JR

'7 Sheets-Sheet 7 Original Filed March 24, 1966 INVENTOR Horace LSm/M,Jr:

ATTORNEYS United States Patent 3,403,454 HEAT TREATING APPARATUS FOR WEBAND SHEET MATERIAL Horace L. Smith, Jr., Richmond, Va., assignor toWhite Consolidated Industries, Inc., a corporation of DelawareContinuation of application Ser. No. 537,132, Mar. 24,

1966. This application Apr. 5, 1967, Ser. No. 628,783

29 Claims. (CI. 34-68) ABSTRACT OF THE DISCLOSURE Fluid supply andradiant heating systems for drying and similar apparatus including mainsupply and return ducts, branch ducts extending transversely across themain ducts, and an arrangement for directing fluid from the branchsupply ducts into contact with the material being treated and forexhausting the fluid and evolved volatiles into the branch exhaustducts. For applications requiring the application of heat to theproduct, radiant heaters may be incorporated in the foregoing structureand a single system may be used to heat the treating fluid and theradiant heaters. Apparatus employing flu-id supply and radiant heatingsystems in accord with the foregoing.

Relation to other applications This application is a continuation ofapplication No. 537,132 filed Mar. 24, 1966, and now abandoned.

In one aspect this invention relates to novel improved fluid supply andradiant heating systems for various types of drying and similarapparatus and, more specifically, to novel improved drying and otherapparatus having fluid supply systems as disclosed herein and to thecombination of radiant heaters with such systems.

The use of air and other fluids to evolve and/or scour away evolvedvolatiles in drying and similar apparatus is a well-known technique asdiscussed in U.S. Patent No. 3,199,213 issued Aug. 10, 1965, to F. H.Milligan et al., for Method of Changing the Moisture Content of Wood,for example. Previously known systems have, however, had a number ofsignificant disadvantages. Among these is an inability to supply thefluid in a manner effective to control the moisture content across theweb or sheet of material being dried, which results in a lack ofuniformity in the processed product.

A further drawback of many previously known dryers is that fluid isdelivered so that it flows parallel to the material being treated at arelative low temperature and velocity. As discussed in the Milliganpatent just mentioned, such dryers are inefficient and uneconomical inaddition to being incapable of providing good control over the treatmentof the material.

Another disadvantage of many heretofore known dryers and similar devicesis that there is a lack of uniformity in the velocity with which thespent fluid and its burden of evolved volatiles is exhausted from thevicinity of the sheet or web being treated and/or the lack of acapability for exhausting the fluid in the immediate area in which itimpinges on the sheet or web. This also results in a nonuniform finalproduct.

A further disadvantage of numerous prior systems is that they are not,as a practical matter, susceptible of being employed in conjunction withradiant heaters. This is a serious deficit since, as pointed out in mycopending application No. 254,674 filed Jan. 29, 1963, for Heat TreatingMethod and Apparatus (which is now abandoned), for example, the combineduse of radiant heating and a scouring gas materially increases theefliciency with which many products may be dried or similarly processed.

Another drawback of many previously known systems is that they are onlyusable in one type of dryer such as a festoon dryer or a tunnel dryer,for example. This makes the design and manufacture of fluid supply andreturn systems relatively expensive as they must be produced onvirtually a custom-made basis.

Yet another disadvantage of heretofore known dryers and similar devicesis in the amount of ductwork required. A related drawback is that suchdevices often require an excessive amount of space to accommodate theductwork and other components of the fluid supply and return system.

One important and primary object of the present invention resides in theprovision of novel improved dryers and similar devices which are free ofthe above-discussed drawbacks of similarly known devices of this type.

A related important and primary object of this invention is theprovision of novel improved fluid supply and return system for dryersand like devices which eliminate the foregoing disadvantages of suchdevices.

The novel fluid and supply return systems of the present invention, bywhich the foregoing and other important objects of this invention areattained, include main supply and return ducts arranged in side-by-sidefashion. A number of branch supply and return ducts extend transverselyacross the two main ducts, supply ducts being alternated with returnducts.

Nozzles or other flow directing members are located at spaced intervalsalong the branch supply ducts to direct the treating fluid from theducts at high velocity (and preferably at high temperature) into contactwith the material being treated. The high velocity fluid evaporatesvolatiles in the material and scours the evolved volatiles away from thesurface of the material to prevent the formation of a stagnant boundarylayer which would materially reduce the evolution of the volatiles.Moreover, the rapid evaporation of the volatiles produces an evaporativecooling effect, which cools and prevents heat damage to the surfaces ofthe material being treated.

Inlets located in the branch exhaust ducts in a similarly spacedarrangement facilitate the removal of the treating fluid and its burdenof evolved volatiles from the dryer or other device. The exhaustarrangement also ensures that the volatiles and treating fluid areexhausted from the vicinity of the web at uniform velocity, contributingfurther to the uniformity of treatment.

In processes involving the application of heat to the product, tubulartype radiant heaters are incorporated in the fluid supply and returnsystems. The legs of the radiant heaters form part of the branch ductwalls, and the fluid supply nozzles and exhaust inlets are fixed to orformed in branch duct wall members fixed between the heater legs. Thisarrangement is highly efficient and compact and yet is relativelyinexpensive to produce.

Multiple pass apparatus branch ducts (and radiant heaters) may belocated on both sides of the main supply and return ducts. Thusarranged, a single unit is capable of heating products in both of thepasses between which it is located and/or of scouring evolved volatilestherefrom, which materially reduces the cost of many forms of dryingapparatus.

The present invention also includes a system for heating both thetreating fluid and the radiant heaters by use of a single liquid heatingunit connected to the radiant heaters and a heat exchanger over whichthe treated fluid is adapted to pass. Provision is made forindependently regulating the flow of the heat transfer liquid throughthe radiant heaters and the heat exchanger so that the radiant heatersand the treating fluid can be maintained at different temperatures. Anarrangement is also preferably provided for recirculating treating fluidfrom the dryer or other treating apparatus to the heat exchanger tominimize the loss of the sensible heat in the treating fluid. Vent andmake-up ducts may also be provided to vary the proportion ofrecirculated fluid and thereby control its content of evolved volatiles.

One important advantage of the novel fluid supply and return system justdescribed is that it may be incorporated in a variety of diflerent typesof dryers and similar devices without modification. Among these arevarious single pass dryers, tunnel dryers, 'festoon dryers and othertypes of multiple pass dryers, and various forms of coating apparatus.

A further important advantage of this system is that it requires muchless space than is commonly required by previously known supply andreturn systems. In part this is due to the partial or total eliminationof external ducts along the dryer or other treating device for supplyingthe treating fluid and to the compactness of the system. Also, asdiscussed above, a single unit can be employed to supply treating fluidto two passes on opposite sides of the unit, resulting in a significantreduction in ductwork and the space required for it.

A significant reduction in size can also be eflected in dryers andsimilar devices by constructing them in accord with the principles ofthis invention because the supply and return units can be arranged toprovide a substantially continuous array of branch supply and returnducts over a given area. This provides substantially more capacity pergiven area than the conventional dryer which employs transverselyextending supply and exhaust plenums located at opposite sides of aradiant heater to supply and carry away the treating fluid.

Another important advantage of dryers and similar devices constructed inaccord with the present invention is that they are capable of producinga more uniform and higher quality product. This is because the fluidsupplied can be uniformly distributed across the product being treated;or the distribution can be selectively regulated to eliminate the wetstreaks which occur in paper drying and similar processes. Uniformity isalso enhanced in the present invention by the continuous removal of thespent drying fluid and its burden of evolved volatiles at a uniformvelocity and closely adjacent its point of impingement on the web. Stillfurther uniformity may be provided by tapering the branch ducts toprovide uniform distribution of the treating fluid to the supply nozzlesand a uniform flow of the spent fluid into the branch return ducts.

Yet another important advantage of this invention is that it provides ahighly eflicient combination of radiant heating and high velocityscouring fluid. This results in significant increases in processingrates in many applications of the present invention such as paperdrying, the drying and curing of coatings, and others.

From the foregoing, it will be apparent that other important objects ofthe present invention reside in the provision of novel, improved fluidsupply and return units for drying apparatus and the like, which:

(1) Can be incorporated in a wide variety of dryers and similar devices.

(2) Require significantly less space than fluid supply and returnsystems heretofore known.

(3) Provide a highly eflicient combination of radiant heating and highvelocity scouring fluid which may also be at a high temperature, therebymaterially increasing the rate at which volatile constituents can beevolved from the product being treated.

(4) Are capable of producing an evaporative cooling efiect whichprevents overheating of the material being treated.

(5) Are capable of providing a uniform or other controlled distributionof treating fluid across the span of the material being treated anduniform exhausting of the spent treating fluid and its burden of evolvedvolatiles from adjacent the vicinity of the web,

(6) Incorporate radiant heaters as integral components.

(7) Are capable of simultaneously supplying radiant heat and treatingfluid to products on opposite sides of the unit.

Still other important objects of the present invention include theprovision of novel, improved dryers and the like which include fluidsupply and return systems and fluid supply-return and radiant heatingsystems constructed in accord with the present invention and which:

(1) Require substantially less space than previously known devices oflike capacity.

(2) In conjunction with the preceding object, require significantly lessductwork than the previously known devices.

(3) In conjunction with the two preceding objects, have alternatingbranch supply and return ducts which virtually continuously span thepass or passes for the material being treated.

(4) Are more eflicient and therefore capable of operating at higherrates than heretofore known units of like capacity.

(5) Are capable of producing a more uniform product of higher qualitythan previously known units.

(6) Include radiant heaters and a fluid heater and a single liquid:heating unit for supplying a heated transfer medium to both the radiantheaters and the fluid heater.

(7) Include an arrangement for recirculating spent treating fluid toretain its sensible heat and vent and make-up systems for controllingthe proportion of recirculated fluid and, therefore, its volatilescontent.

Other objects, additional advantages, and further important features ofthe present invention will become more fully apparent from the appendedclaims and as the ensuing detailed description and discussion proceedsin conjunction with the accompanying drawing, wherein:

FIGURE 1 is a diagrammatic section through a novel, improved dryerconstructed in accord with the principles of the present invention;

FIGURE 2 is a section through a novel, improved fluid supply-return andradiant heating unit constructed in accord with the principles of thepresent invention;

FIGURE 3 is a section through the dryer of FIGURE 1, taken substantiallyalong line 33 of the latter figure;

FIGURE 4 is a section through the unit of FIGURE 2, taken substantiallyalong line 4-4 of the latter figure;

FIGURE 5 is a section through the unit of FIGURE 2, taken substantiallyalong line 5-5 of the latter figure and showing the ports providingcommunication between main supply and return ducts and brach supply andreturn ducts incorporated in the latter;

FIGURE 6 is a diagrammatic illustration of the main system duct workwhich may be employed in delivering the fluid to and exhausting spentfluid from the main supply and return ducts of the fluid supply-returnand radiant heating units;

FIGURE 7 is a diagrammatic view of a system for heating the treatingfluid and the radiant heaters and for circulating the treating fluidthrough the supply-return and radiant heating units;

FIGURE 8 is a partly diagrammatic section through a multiple pass dryer,illustrating the arrangement and type of fluid supply-return and radiantheating units employed in apparatus of this type;

FIGURE 9 is diagrammatic view, partly sectioned, of coating apparatusequipped with fluid supply-return and radiant heating units constructedin accord with the principles of the present invention; and

FIGURE 10 is a diagrammatic sectional view through a novel, improvedtunnel dryer equipped with fluid supplyreturn and radiant heating unitsconstructed in accord with the principles of the present invention.

Referring now to the drawing, FIGURE 1 depicts a novel, improved singlepass dryer 20 which features fluid supply-return and radiant heatingunits 22 constructed in accord with the principles of the presentinvention for dryig the product to be treated. Dryer 20 also includes aseries of parallel, spaced apart, rotatably mounted rolls 24establishing a path 26 for the product or material being dried, which isin the form of a web 28. As shown in FIGURE 1, units 22 are located onboth sides of path 26 to dry web28 by simulataneously applying radiantheat to both sides of the web to evolve volatiles from it. Units 22 alsodirect air or other treating fluid at high velocity into contact withthe sides of the web to assist in evolving the volatiles and to scouraway evolved volatiles from adjacent its surfaces. The high velocityfluid prevents retardation of the drying process by eliminating theformation of a stagnant layer adjacent the web and, in addition, causesevaporative cooling adjacent the surfaces of the material being treatedand thereby prevents it from being overheated. It is preferred that thetreating fluid also be heated, preferably to a temperature typically onthe order of 300 to 650 F. since, as explained in the Milligan patentmentioned above, hot, high velocity air is a highly effective dryingagent; and the same is true for other treating fluids.

Referring now to FIGURES 24, each of the novel fluid supply-return andradiant heating units 22 incorporated in dryer 20 includes a main ductpair consisting of elongated main supply and return ducts 30 and 32separated by a common dividing wall 34. The main ducts 30 and 32 extendlengthwise of dryer 20 with two main duct pairs above and two below thepath 26 of the product being dried. The two main duct pairs above path26 are arranged in end-to-end relationship as are the main duct pairsbelow path 26. Thus, dryer 20 employs four fluid supply-return andradiant heating units, two of these being arranged in end-to-endrelationship above path 26 and two similarly arranged below the path.

Referring now specifically to FIGURE 2 and 4, each of the units 22includes a number of branch supply and return ducts 36 and 38 extendingtransversely across the associated main supply and return ducts 30 and32. As shown in FIGURE 4, the main and branch ducts are integral, thecommon top wall 48 of the main ducts forming the bottom walls for thebranch ducts and the side walls of the main ducts forming the end wallsfor the branch ducts. Branch supply ducts are alternated with branchreturn ducts (see FIGURES 4 and 5); and the branch return ducts arearranged with their side walls 42 in abutting relationship (see FIGURE2).

Branch supply ducts 36 communicate with main supply ducts 30 throughapertures 44 (see FIGURE 5) in the common wall 40 between the main andbranch ducts adjacent the wall 34 separating the main supply and returnducts. Branch return ducts 38 similarly communicate with main returnduct 32 through apertures 46 in common wall 40 on the side of commonpartition 34 opposite apertures 44.

Air or other treating fluid is accelerated and directed normally at highvelocity (typically on the order of 2,000- 15,000 feet per minute)against web 28 by nozzles 48 fixed to the top wall 50 of each branchsupply duct 36. The nozzle inlets communicate with the interior of theduct through apertures 52 in its top wall 50. As shown in FIGURE 3,nozzles 48 are disposed in spaced apart relationship the length of eachof the branch supply ducts 36. The treating fluid exiting from nozzles48 contacts the surfaces of web 28 at high velocity, scouring away fromthe surfaces volatiles evolved from the web. The spent fluid, togetherwith its burden of evolved volatiles, flows into branch return ducts 38through inlet apertures 54 (see FIGURE 4) formed in the top walls 56 ofthe branch return ducts.

It will be apparent, from the foregoing, that a uniform distribution ofthe treating fluid across the span of web 28 can be provided byuniformly spacing nozzles 48 the length of branch supply ducts 36.Similarly, where desired, controlled nonuniform distribution of thetreating fluid can be provided by appropriate spacing of the nozzles.For further control over the distribution of the treating fluid againstweb 28, dampers or other flow control members (not shown) may be locatedat the inlet ends of nozzles 48.

Another important feature of the arrangement just described is that theinlets 54 to branch return duct 38 are distributed uniformly the lengthof the branch duct and are adjacent supply nozzles 48. This insures thatthe spent treating fluid, together with its burden of evolved volatiles,flows with uniform velocity into the return ducts over the entire lengththereof and that the spent fluid flows into these ducts at pointsclosely adjacent those at which it impinges upon the web being treated.This provides uniform exit velocities for the spent fluid, which furtherinsures uniform treatment of the web being dried. For other than uniformdistributions of the treating fluid, the exhaust openings can of coursebe spaced at varied intervals like nozzles 48.

As discussed above, it is important that the treating fluid be directedat high velocity against the material being treated as low velocityfluid is not effective to scour away evolved volatiles or to causeevaporative cooling of the material. Typically, the impingement velocitywill be on the order of 2,000-15,000 feet per minute as mentioned above.Even higher velocities may be beneficially employed, however, toincrease the scouring and evaporative cooling effect. The onlysignificant limitations on this velocity are the ability of the materialbeing treated to withstand the impact of the fluid and the expense ofproviding equipment capable of delivering fluid at extremely highvelocities.

As discussed above, volatiles may be evolved from the web 28 beingtreated merely by supplying air or other treating fluid at high velocityand high temperatures through nozzles 48. However, in the preferredembodiment of the present invention, volatiles are evolved much morerapidly, thereby materially increasing the efliciency of units 22, byincorporating in them one or more tubular type radiant heaters 58. Eachheater consists of a plurality of parallel, spaced apart, straight legs60 (see FIGURES 3 and 5) having coplanar centerlines and extending inthe same direction as branch ducts 36 and 38. The legs 60 are connectedby end bends 62 alternately located at opposite ends of the heater.

As is best shown in FIGURE 2, legs 60 of the radiant heater partiallydefine the top walls 50. and 56 of branch supply and return ducts 36 and38, respectively; and alternate legs 60 also partially define the sidewalls of the branch ducts, being welded to branch duct wall members 42of the latter. The configurations of the branch duct top walls 50 and 56are completed by wall members 64 and 66, respectively, which are weldedor otherwise fixed between adjacent radiator legs 60. As shown in FIGURE2, fluid supply nozzles 48 are fixed to branch duct wall members 64; andthe inlet apertures to branch return ducts 38 are formed in wall members66 so that, as shown in FIG- URE 3, the rows of nozzles 48 and exhaustapertures 54 are disposed between adjacent legs 60 of the radiantheater.

In the particular embodiment of the invention illustrated in FIGURES2-4, there are two rows of supply nozzles 48 associated with each branchsupply duct 36 and two rows of inlet apertures to branch return duct 38associated with each of the branch return ducts. The number of rows mayof course be varied as desired; but it is preferred that a single ordouble row of apertures be used since this insures a row of inletapertures adjacent each row of nozzles. As discussed above, thisadjacent relationship is important in obtaining uniform exit velocitiesfor the treating fluid by removing it from adjacent the surface of thematerial being treated as near as possible to the area at which thefluid impinges upon the web being treated.

Referring next to FIGURES 6 and 7, the treating fluid is supplied to themain supply duct 30 in each unit 22 by a blower 68 connected through aduct 70 to a fluid heater 7 72. As it flows through the fluid heater,the treating fluid is heated as it flows over a heat exchanger 74. Fromfluid heater 72, the heated treating fluid flows through a main systemsupply duct 76 and branch system supply ducts 78 into the main suplyducts 30 of units 22 (see also FIG- URE 6), the branch system ductsbeing connected to the main unit ducts at about the midpoint of thelatter. Similarly, the spent treating fluid and its burden of evolvedvolatiles flows from branch return ducts 38 of the various units 22through ports 46 into the associated main unit return ducts 32. Fromthese ducts, the spent fluid and its burden flows through branch systemreturn ducts 80 into main system return ducts 82.

As discussed previously, in the present invention, main system returnducts 82 are preferably connected to the inlet of circulating blower 68so that the spent treating fluid may be recirculated through the system,thereby eliminating the loss of sensible heat which would result if thespent fluid were discharged from the system.

In many applications of the present invention, such as in the drying ofpaper, for example, the percentage of moisture or other volatiles in thetreating fluid must be closely controlled to produce the desiredcharacteristics in the treated product. To permit such control, mainsystem return duct 82 is provided with a make-up duct 84; and a ventduct 86 is located in the duct 70 between blower 68 and fluid heater 72.Valves 88 and 90 control the flow through make-up and vent ducts 84 and86, respectively. By properly adjusting valves 88 and 90, the properproportion of spent recirculated fluid can be discharged from the systemand replaced with treating fluid having a lower content of volatiles tomaintain the volatile content at the desired level. Valves 88 and 90 maybe adjusted manually or, if desired, may be automatically controlled bya control system of the type disclosed in my US. Patent No. 3,208,158issued Sept. 28, 1965, for Dryers.

Referring now to FIGURE 7, the heat exchanger 74 in fluid heating unit72 and radiant heaters 58 are of the type through which a heated fluidheat transfer medium is circulated to elevate them to the desiredtemperature. The preferred heat transfer mediums are high boiling pointorganic liquids and eutectic mixtures of inorganic salts, which can becirculated at extremely high temperature in liquid form. Suitable mediaof this type are discussed in detail in my copending application Ser.No. 323,848 flled Nov. 14, 1963 for Heat Exchangers, which is herebyincorporated by reference in this application.

The advantage of employing liquid heat transfer media is that theproblems appurtenant to the high pressures associated with hightemperature steam are eliminated and yet the radiant heaters and thetreating fluid may be heated to temperatures of several hundred degreesFahrenheit.

The system illustrated in FIGURE 7 for heating and circulating theliquid heat transfer medium includes a storage tank 92 from which theliquid can be pumped by a transfer pump 94 through a conduit 96 to adrain 98 or to the main circulation system, which includes main returnand supply conduits 100 and 102 and is a closed loop through which theliquid is circulated by a main circulation pump 104.

From main return conduit 100 the heat transfer liquid flows into aliquid heating unit 106 where it is heated to the desired temperature.This unit may be of any desired construction and includes a temperatureresponsive controller 108 which so regulates the flow of fuel to theheating unit through conduit 110 as to maintain the temperature of theheated liquid flowing into main supply conduit 102 constant.

From main supply conduit 102, part of the heated liquid flows throughbranch supply conduit 112 to the heat exchanger 74 in fluid heater 72.The volume of flow through conduit 112 is controlled by temperatureresponsive controller 114, which is connected to a valve 116 in conduit112 and has a sensor (not shown) in the main system fluid supply duct76. Controller 114 regulates valve 116 so as 8 to maintain thetemperature of the treating fluid flowing into main system supply duct76 constant. From fluid heating unit 72, the heat transfer liquid flowsthrough branch return conduits 118 and 120 back into main return conduit100.

Referring now to FIGURES 3 and 7, part of the heated heat transferliquid flowing through main supply conduit 102 is diverted throughbranch supply conduit 122 to the radiator or radiators 58 of the dryerin which they are incorporated. From supply conduit 122, the heatedliquid is pumped through the radiator or radiators 58 in each zone ofthe dryer by an independent zone pump 124 (only one of which is shown)with its outlet connected to the radiator or radiators and its inletconnected to conduit 122 by a branch supply conduit 126.

As shown in FIGURE 3, each radiator 58 is connected, at its outlet end,to a branch return conduit to recirculate the liquid to the heatingunit. Each branch circulation system also includes a branch bypassconduit 132 connected between its branch inlet conduit 126 and a branchreturn conduit 134 connected between radiator 58 and return conduit 130.Flow through bypass conduit 132 is regulated by a three-way valve 136which, in turn, is adjusted by a temperature responsive controller 138with its temperature responsive probe located on the side of radiator 58facing the product to be treated.

As long as radiator 58 remains at the desired temperature, pump 124circulates the heat transfer liquid through the closed branch loopconsisting of conduit 126, radiator 58, and bypass conduit 132. When thetemperature of the radiator starts to drop, controller 138 adjusts valve136 to divert less liquid through bypass conduit 132 and more intoreturn conduit 130. This permits fresh, hotter liquid to flow fromconduit 122 into the branch system to bring radiator 58 back to thedesired temperature.

One of the important features of the fluid circulation system justdescribed is that the temperature of the heat exchanger 74 in fluidheating unit 72 and the temperatures of radiators 58 can beindependently regulated. This permits the temperatures of thesecomponents to be so adjusted that the radiant energy supplied by theradiators will be at the most eflective wave length range and thetreating fluid will be at the optimum temperature.

Where more than one radiator 58 is employed in each zone, each radiatorcan be connected in parallel between supply and return conduits 122 and130 in the manner just described as shown in FIGURE 3. This is animportant practical feature of the present invention inasmuch as itpermits independent control of the radiator temperatures in succeedingzones of the dryer in which they are incorporated, adding to theflexibility of the dryer.

Inasmuch as the details of the fluid heating and circulating system justdescribed such as the bypass system 140 provided to maintain constantflow through heating unit 106 are not by themselves part of the presentinvention, it is not considered necessary to describe them furtherherein. Systems of the type just described are discussed in more detailin my US. Patent No. 3,236,292 issued Feb. 22, 1966, for Dryers, whichis hereby incorporated by reference herein.

The novel fluid supply-return and radiant heating units discussed abovemay be employed in various types of multiple pass driers as Well as thesingle pass type described above. One type of multiple pass dryer inwhich such units may be incorporated is the festoon or multiple runvertical dryer 142 of FIGURE 8.

Dryer 142 includes a plurality of rotatably supported rolls 144 arrangedin upper and lower rows 146 and 148. The rolls in upper row 146 aredirectly above the spaces between the rolls in lower row 148 to directthe web 150 of product to be treated through the dryer in a plurality ofparallel, spaced apart passes 152 extending between the two rows ofrolls. As the web of product 150 moves through dryer 142, it is driedand evolved volatiles are carried away from it by fluid supply'returnand radiant heating units 154 and 156 oriented adjacent and parallel topasses 152 so that the centerlines of the radiant heater legs lie inplanes parallel to the passes and the fluid supply nozzles are at equaldistances from the passes. Units 154, which are located outside theoutermost pass 152, may be identical to the units 22 described above.These units are oriented with their nozzles and radiant heaters facingthe pass 152 adjacent which they are located.

The fluid supply-return and radiant heating units 156 are each locatedbetween a pair of adjacent passes 152 and, like units 154, extendgenerally from one row of roll 144 to the other. Units 156 are identicalto those described previously except that there are branch ducts andradiant heaters on both sides of the main duct pairs in these units, thearrangement of these components on both sides of the main duct pairsbeing identical. This modification adapts each unit 156 forsimultaneously heating and scouring volatiles from portions of web 150in two passes on opposite sides of the unit. Thus, the combination ofunits 154 and 156 insures that, in each of the passes 152, both sides ofweb 150 are simultaneously radiantly heated and contacted by highvelocity fluid to assist in evolving volatiles and to scour away thosevolatiles which have evolved While preventing overheating of the web.

As shown in FIGURE 8, between or adjacent each of the passes 152, thereare two fluid supply-return and radiant heating units 154 or 156connected in end-to-end relationship. This arrangement divides dryer 142into an upper zone 158 and a lower zone 160. If desired, temperaturesand other parameters may be varied in each of these zones for aparticular application of dryer 142. Control of the radiant heatertemperature is readily accomplished by the control arrangementillustrated in FIG- URES 3 and 7. Similarly, the temperature, velocity,etc. of the treating fiuid can readily be controlled by installing flowcontrol dampers, which may be temperature responsive, in the branchsystem supply ducts 162 through which the treating fluid is supplied tounits 154 and 156.

As mentioned previously and as shown in FIGURE 8, dryer 142 is of thevertical run type. However, it will be readily apparent to those skilledin the arts to which this invention relates that the arrangement offluid supplyreturn and radiant heating units illustrated in FIGURE 8 isequally adaptable to a multiple run drier of the horizontal type.

FIGURE 9 illustrates the application of the principles of the presentinvention to coating apparatus identified generally by referencecharacter 164. This apparatus includes an unwind stand 166 from whichthe web 168 to be coated is fed through the coating apparatus. Fromstand 166, the web passes through a conventional coating station 170where the desired coating material is applied to one side 172 of theweb. From the coating station, the web passes over a series of rotatablysupported rolls 174, which define a path 176 for the web and arepreferably arranged to periodically change the direction of web andthereby prevent high speed flutter in the manner discussed in my US.Patent No. 3,228,114 issued Jan. 11, 1966, for Multiple Run Drier. Asshown in FIGURE 9, only the uncoated side of the web contacts rolls 174.

As the coated web moves through pass 176, the coating is cured or driedby radiant energy and high velocity heated air or other fluid emanatingfrom fluid supplyretnrn and radiant heating units 178, which may beidentical to the corresponding units 22 and 154 described above. Fromthe last path defining roll 174, the finished web 168 is led over adirection changing roll 180 to a rewind stand 182.

Coating apparatus 164 may be supplied with a heat transfer liquid forthe radiant heaters in units 178 and a heating unit for the treatingfluid in the same manner as the dryer 20 illustrated in FIGURE 1 and thefestoon dryer 142 illustrated in FIGURE 8.

FIGURE illustrates the application of the principles of the presentinvention to a dryer 184 of the tunnel type. Tunnel dryers are commonlyemployed for drying wallboard, veneers, and similar relatively thickproducts.

As shown in FIGURE 10, a tunnel dryer typically includes a casing 186with a product inlet 188 in one end wall 190 and an outlet 192 in theopposite end wall 194 for the product 196 being treated. As the web orsheet of product 196 moves through casing 186, it is supported by anendless belt 198 trained around rotatably supported rolls 200 and 202 atopposite ends of the casing.

During its passage through the casing, the product 1% is dried byradiant heat and high velocity air or other fluid from fluidsupply-return and radiant heating units 204, which may be identical tothose described previously. As shown in FIGURE 10, units 204 are locatedclosely adjacent and both above and below the path 206 of the materialthrough the dryer so that it is simultaneously heated from both sides.As is also shown in FIGURE 10, units 204 extend substantially the entiredistance between the rolls and 202 at opposite ends of the casing 186;and two (or even more) units are arranged in end-to-end relationship tospan this distance. As discussed in conjunction with the embodiment ofthe present invention illustrated in FIGURE 8, this divides the dryerinto zones in which different temperature and other conditions may bemaintained.

Because of their uncommon thickness, products of the type dried intunnel dryers are subject to curling, cockling and other forms ofwarpage. To prevent this, the product 196 being dried may be maintainedflat as it moves through casing 186 by a second, upper endless belt 208trained around rolls 210 and 212 at opposite ends of the casing aboverolls 200 and 202. For products which are not subject to such warpagethe upper belt may, of course, be omitted.

As shown in FIGURE 10, belts 198 and 208 pass between units 204 and theproduct 196 being dried. These belts are therefore preferably of an openmesh construction so that the radiant energy and the treating fluid canpenetrate to the product through the belt and so the fluid and itsburden of evolved volatiles can pass back through the belt into thefluid return ducts of units 204.

The details of the tunnel dryer are not, by themselves, part of thepresent invention; and it is therefore not considered necessary todiscuss them further herein. Tunnel dryers of the type illustrated inFIGURE 10 are disclosed in detail in my copending application No.530,146 filed Feb. 25, 1966, for Apparatus, which is hereby incorporatedby reference.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come Within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. Multiple run treating apparatus for continuous webs, comprising:

(a) a plurality of rotatably supported rolls in two parallel, spacedapart rows defining a plurality of parallel, spaced apart passesextending from one to the other of said rows for a web trainedalternately over succeeding rolls in alternate ones of said rows; and

(b) a ventilating system for effecting a flow of fluid into contact withthe surfaces of said web as it moves through each of said passes, saidventilating system including:

(0) a plurality of main duct pairs each including a main supply duct anda main return duct arranged in side-by-side relationship, there beingduct pairs between adjacent passes and adjacent the outer sides of theoutermost passes;

(d) branch supply and return ducts extending across and communicatingwith the main supply and return duct in each main duct pair;

(e) fluid supply means at spaced intervals along each said branch supplyduct and communicating therewith for directing fluid from the associatedbranch supply duct toward the pass thereadjacent; and

(f) at least one fluid inlet to each branch return duct for fluid fromthe pass thereadjacent;

(g) there being branch supply and return ducts on both sides of the mainduct pairs between passes and on the sides of the outer main duct pairsfacing the outermost passes, whereby fluid is supplied to and removedfrom both sides of each pass.

2. The apparatus of claim 1, together with a tubular radiant heater oneach side of the main duct pairs between passes and on the sides of theouter main duct pairs facing the outermost passes for heating the webmoving through said passes from both sides thereof.

3. The apparatus of claim 1, wherein there are plural main duct pairsbetween adjacent passes and adjacent the other sides of the outermostpasses and independent fluid supply and return means for each of saidmain duct pairs, thereby dividing the passes between said rows of rollsinto a plurality of zones.

4. Coating apparatus for web material, comprising:

(a) means for applying a coating material to one side of the web to becoated; and

(b) means for curing said coating including:

(c) a plurality of parallel, spaced apart rolls establishing a pass forthe coated material and adapted to support the uncoated side of saidmaterial, and

(d) a radiant heating and ventilating system on the opposite side of thepass from said rolls including:

(e) a tubular radiant heater closely adjacent and generally parallel tothe pass for the coated material;

(f) branch supply and return ducts extending transversely of said passon the opposite side of the radiant heater therefrom;

(g) fluid supply means at spaced intervals along said branch su plyducts for directing fluid from said branch supply ducts into contactwith the coated side of said material;

(h) at least one fluid inlet to each of the branch return ducts; and

(i) means including main supply and return ducts on the side of thebranch ducts opposite the radiant heater for supplying fluid to andevacuating it from the branch supply and return ducts, respectively.

5. A radiant heating and fluid supply system, compris- (a) a tubularradiant heater having a plurality of elongated, spaced apart legs;

(b) a plurality of branch supply and return ducts dis posed inside-by-side relationship;

(c) means for supplying fluid to said branch supply ducts including amain supply duct, said branch supply and return ducts extending acrossthe main supply duct at intervals therealong and communicatingtherewith;

(d) the side walls of the branch supply and return ducts being fixed tolegs of said radiant heater and the walls of said ducts opposite themain supply duct comprising said heater legs and wall members fixed toand between said heater legs;

(e) fluid discharge means at spaced intervals along said branch supplyducts and communicating therewith for discharging fluid from each saidbranch supply duct to the area thereadjacent; and

(f) at least one inlet to each of said branch return ducts.

6. The radiant heating and fluid supply system of claim 5, wherein:

(a) at least one of the wall members forming the said opposite wall ofeach of the plural supply ducts has a row of spaced apart aperturestherein; and

(b) said fluid discharge means comprise nozzles fixed to said supplyducts and communicating with the interiors thereof through the aperturesin said wall members.

7. The radiant heating and fluid supply system of claim 6, wherein:

(a) the said opposite walls of said supply ducts include plural wallmembers; and

(b) there is a row of said nozzles fixed to each of said wall members.

8. The radiant heating and fluid supply system of claim 6, wherein thefluid inlets to the return ducts are apertures in the wall membersforming the said opposite sides of said return ducts.

9. Apparatus for treating web and sheet material and the like,comprising:

(a) a fluid supply system which includes:

(b) at least three main duct pairs, each of which comprises a mainsupply duct and a cooperating main return duct, the ducts in each pairbeing arranged in side-by-side relation and the main duct pairs beingdisposed in parallel spaced apart relationship to provide at least twopasses through the apparatus for the material to be treated;

(c) branch supply and return ducts extending transversely of and acrosssaid passes between said main ducts and the passes thereadjacent andcommunicating with the main supply and return ducts, there being a firstseries of branch supply and return ducts on one side of each inner mainduct pair and a second series of branch supply and return ducts on theopposite side of each said inner main duct pair and a single series ofbranch supply and return ducts associated with each of the outer mainduct pairs, said single series of branch ducts being on the side of theouter duct pair facing the adjacent inner duct pair, whereby the branchducts define and are located on both sides of each of the passes throughsaid apparatus;

(d) fluid discharge means at spaced intervals along the branch supplyducts for effecting flows of fluid from said branch supply ducts towardthe passes for the material to be treated;

(e) inlets to said branch return ducts facing the passes for thematerial to be treated; and

(f) means for guiding the material to be treated through said apparatusby way of the passes between said branch ducts.

10. A radiant heating and fluid supply system, comprising:

(a) a tubular radiant heater having a plurality of spaced apart legs,the centerlines of the radiant heater legs being parallel and lying inthe same plane and said legs being connected into a single fluid channelby end bends joining adjacent legs and alternately located at oppositeends of said legs;

(b) a plurality of branch supply and return ducts all lyingsubstantially to one side of said heater, said branch supply and returnducts all being disposed in side-by-side relationship and branch returnducts being alternated with branch supply ducts;

(c) fluid discharge means at spaced intervals along said branch supplyducts and communicating there with for discharging fluid from saidbranch supply ducts to the areas thereadjacent;

(d) at least one fluid inlet to each of the branch return ducts; and

(e) main supply and return ducts extending transversely of said branchsupply and return ducts on the side thereof opposite said heater.

11. Heat treating apparatus for web and sheet material and the like,comprising:

(a) means establishing a path for the material to be treated; and

(b) at least one radiant heating and fluid supply system locatedadjacent said path and comprising:

(c) a tubular radiant heater having a plurality of spaced apart fluidconducting legs;

(d) a plurality of branch supply and return ducts all lyingsubstantially to one side of said radiant heater, said branch supply andreturn ducts being arranged in side-by-side relationship and said branchsupply ducts being alternated with said branch return ducts;

(e) said supply and return ducts all having wall members opposed to thepath of the material to be treated and the exposed surfaces of said wallmembers all lying in a common plane more remote from said path than theportions of said radiant heater fluid conducting legs, whereby said legsare exposed to thereby emit radiant energy directly to the material tobe treated;

(f) fluid discharge means at spaced intervals along said supply ducts,each said fluid discharge means being oriented to effect a flow of fluidfrom the associated supply duct toward the path of the material to betreated;

(g) at least one inlet to each of said return ducts, each said inletfacing the path of material to be treated and said inlets being spacedaway from said path; and

(h) means for supplying fluid to the supply ducts.

12. The apparatus of claim 11, wherein there are radiant heating andfluid supply units on both sides of the'path of the material beingtreated for simultaneously treating both sides of said material.

13. The apparatus of claim 11, wherein the centerlines of the radiantheater legs lie in at least one plane, each said plane being parallel tothe path of the product through the treating apparatus, whereby there isa substantially uniform distribution of radiant energy from said heaterto the product being treated.

14. The heat treating apparatus of claim 11, together with:

(a) main supply and return ducts extending along and adjacent the pathof the material to be treated and on the opposite sides of the branchducts therefrom; and

(b) means providing fluid communication between the main supply duct andthe branch supply ducts and between the branch return ducts and the mainreturn duct.

15. The heat treating apparatus of claim 11, wherein the branch ductsare arranged in abutting relationship.

16. The heat treating apparatus of claim 14, wherein each said fluiddischarge means comprises an aperture extending through the sides of thebranch supply ducts opposite said main ducts.

17. The heat treating apparatus of claim 14, wherein there are aplurality of independent fluid inlets to each of said branch returnducts, said inlets being in and spaced along the sides of said branchducts opposite the main ducts.

18. The heat treating apparatus of claim 14:

(a) wherein the main supply and return ducts are arranged inside-by-side relationship; and

(b) there are plural pairs of main ducts, each including a main supplyduct and a main return duct cooperating therewith.

19. The heat treating apparatus of claim 18, wherein the main duct pairsare disposed in parallel spaced apart relationship to provide at leastone pass through the apparatus for the material to be treated.

20. The heat treating apparatus of claim 18, wherein the main duct pairsare arranged in end-to-end relationship.

21. The heat treating apparatus of claim 18, together with:

(a) means for supplying fluid to said main supply ducts including a mainsystem supply duct and a branch system supply duct connected between themain system supply duct and each of the aforesaid main supply ducts; and

(b) a main system return duct and branch system return ducts connectedfrom each of the aforesaid main return ducts to the main systemreturnvduct.

22. The heat treating apparatus of claim 18, together with:

(a) fluid circulating means having an inlet and an outlet;

(b) first duct means connecting said outlet to said main supply duct;and

(c) second duct means connecting said main return duct to the inlet ofthe fluid circulating means for returning fluid thereto.

23. The heat treating apparatus of claim 22, together with:

(a) a fluid vent duct connected to said second duct means;

(b) a fluid make-up duct connected to said first duct means; and

(c) selectively adjustable valves in said vent and makeup ducts foradjusting the amount of fluid respectively discharged and admittedthrough the vent and make-up ducts, respectively.

24. The heat treating apparatus of claim 22, together with a fluidheater interposed in said first duct means for heating the fluid flowingto said main supply duct.

25. Heat treating apparatus for web and sheet material and the like,comprising:

(a) means establishing a path for the material to be treated, said pathestablishing means providing at least two path segments extending indifferent directions; and

(b) at least one radiant heating and fluid supply system locatedadjacent said path and comprising:

(c) a tubular radiant heater having a plurality of spaced apart fluidconducting legs associated with each of said segments, the cen-terlinesof the legs of each said radiant heater lying in at least one planewhich is parallel to the path of the product through the segment withwhich the radiant heater is associated;

(d) a plurality of supply and return ducts all lying substantially toone side of each said radiant heater, said branch supply and returnducts being arranged in side-by-side relationship and branch supplyducts being alternated with branch return ducts;

(e) fluid discharge means at spaced intervals along said supply ducts,each said fluid discharge means being oriented to effect a flow of fluidfrom the associated supply duct toward the path of the material to betreated;

(f) at least one inlet to each of said return ducts, each said inletfacing the path of material to be treated and said inlets being spacedaway from said path; and

(g) means for supplying fluid to the supply ducts.

26. Treating apparatus for web and sheet type material, comprising:

(a) an elongated casing having inlet and outlet openings at the oppositeends thereof for the material to be treated;

(b) means for supporting said material as it moves through said casingcomprising rolls at the opposite ends of said casing adjacent saidopenings and an endless, flexible, open mesh belt trained around saidrolls to provide material supporting and return legs; and

(c) a ventilating system for effecting a flow of fluid into contact withsaid material as it moves through said casing, including:

((1) co-operating main supply and return ducts extending lengthwise ofsaid casing and located between the legs of said belt;

(e) branch supply and return ducts between said main ducts and thematerial supporting leg of said belt, said branch ducts extendingtransversely in the casing across the main ducts and communicatingtherewith, the sides of the branch ducts opposite the main ducts beingadjacent and parallel to the path of the material through said casing;

(f) fluid supply means at spaced intervals along each of said branchsupply ducts for directing fluid from the associated duct through theopenings in said belt toward the material being treated; and

(g) at least one fluid inlet to each branch return duct.

27. Treating apparatus for web and sheet type material,

comprising (a) an elongated casing having inlet and outlet openings atthe opposite ends thereof for the material to be treated;

(b) means including a first set of rolls and a first belt of open meshconstruction trained therearound to provide a material bearing leg forsupporting said material as it moves through said casing; and

(c) a ventilating system for effecting a flow of fluid into contact withsaid material as it moves through said casing, including:

(d) -co-operating main supply and return ducts extending lengthwise ofsaid casing;

(e) branch supply and return ducts between said main ducts and the pathof the material through the casing, said branch ducts extendingtransversely in the casing across the main ducts and communicatingtherewith, the sides of the branch ducts opposite the main ducts beingadjacent and parallel to the path of the material through said casing;

(f) fluid supply means at spaced intervals along each of said branchsupply ducts for directing fluid from the associated duct toward thematerial being treated;

(g) at least one fluid inlet to each branch return duct;

(h) means for preventing wrinkling, cockling, and other distortions ofthe material being treated as it moves through said casing including asecond set of rolls adjacent the first set of rolls and a second endlessbelt of open mesh construction trained around the second set of rollsfor pressing said material against the material bearing leg of the firstbelt; and

(i) a second ventilating system as aforesaid between the legs of thesecond belt for effecting a flow of fluid into contact with the side ofthe material opposite that facing the first ventilating system.

28. Treating apparatus for web and sheet type material,

comprising ing, said branch ducts extending transversely in the casingacross the main ducts and communicating therewith, the sides of thebranch ducts opposite the main ducts being adjacent and parallel to thepath of the material through said casing;

(f) fluid supply means at spaced intervals along each of said branchsupply ducts for directing fluid from the associated d-uct toward thematerial being treated;

(g) at least one fluid inlet to each branch return duct;

and

(h) radiant heater means between the main duct pairs and the materialsupporting leg of the endless belt for supplying radiant energy throughopenings in said belt to said material.

29. Heat treating appanatus for web and sheet material and the like,comprising:

(a) means establishing a path for the material to be treated;

(b) at least one radiant heating and fluid supply system locatedadjacent said path and comprising:

(c) a radiant heater means;

(d) fluid supply and return ducts extending across said path atintervals therealong;

(e) fluid supply means at spaced intervals along each said supply ductfor directing fluid from the associated duct toward the path of thematerial to be treated;

(f) at least one inlet to each of said return ducts, each said inletfacing the path of material to be treated; and

(g) means including a fluid heating unit having a heater therein forsupplying heated fluid to said supply ducts; and

(h) means including a single heating unit for eflecting a flow of aheated heat transfer medium through said radiant heater means and theheater of said fluid heating unit, said last-named means including firstand second temperature responsive means for independently controllingthe flow of the heat transfer medium through said radiant heater meansand the heater of said fluid heating unit, respectively, and therebyindependently regulating the temperature of said radiant heater meansand the heater of the fluid heating unit.

References Cited UNITED STATES PATENTS 2,900,738 8/1959 Ofien 34-155 XR3,084,448 4/1963 Dungler 34-155 2,229,285 1/ 1941 Gehnrich 34-160 XR2,389,586 11/1945 Andrews 34-68 2,473,629 6/1949 Andrews 263-3 2,896,3356/ 1959 Dungler 34-68 3,065,686 11/1962 Geocaris 98-40 3,208,158 9/1965Smith 34-122 3,23 6,292 2/ 1966 Smith -11 3,254,422 6/ 1966 Deflel 34-18FOREIGN PATENTS 639,183 11/ 1936 Germany.

FREDERICK L. MATTESON, 111., Primary Examiner.

H. B. 'RAMEY, Assistant Examiner.

